18 persons were killed after lightning struck them across eight districts in the state. Five persons were killed in separate incidents of wall collapse in West Champaran district.
The state government has announced a compensation of Rs four lakh each to the affected families.
A cyclonic circulation prevailing in the upper air (1.5 km above the surface) over Bihar caused Sunday's storm. Also, a low pressure area has developed over the Bay of Bengal, leading to moisture incursion in Bihar causing rainfall.
"Several parts of Bihar are expected to receive rainfall and witness thunderstorms till May 30," said S.K. Patel, meteorologist at the Patna Met office.
Even Patna witnessed 10.5 mm rainfall on Sunday over more than 30 minutes in the afternoon. The state capital has so far received 49.4 mm of pre-monsoon rainfall (from March 1 to May 31), a notch below the normal (51. 0 mm).
The state till May 28 had received 106.7 mm of rainfall, almost 50 per cent more than the normal pre-monsoon rainfall. Other places which recorded rainfall on Sunday were West Champaran, East Champaran, Darbhanga, Sitamarhi and Madhepura among others.
Gusty winds, blowing at a speed of around 50 km per hour, accompanied the rainfall, which led to the outages in Patna. A senior official at the Patna electric supply undertaking said that no major damage was done to the distribution line and power supply was restored in less than an hour.
The Patna Met office said the depression over east-central Bay of Bengal is likely become a deep depression in the next 12 hours and then into a cyclonic circulation in 24 hours. The conditions, the Met office said, were favourable for further advancement of the southwest monsoon into parts of southeast Arabian Sea and the Bay of Bengal in the next 24 hours.
The met office has forecast timely arrival of monsoon in Bihar. The usual monsoon arrival date for Bihar is June 10.
(With inputs from The Telegraph Calcutta)